#include <cstdio>
int main()
{
    int c1,c2;
    scanf("%d %d",&c1,&c2);
    int total;
    int secs,mins,hors;
    total=c2-c1;
    if(total%100<45)
    {
        total/=100;
    }else{
        total=total/100+1;
    }
    secs=total%60;
    total/=60;
    mins=total%60;
    total/=60;
    hors=total;
    printf("%02d:%02d:%02d\n",hors,mins,secs);
    return 0;
}
